We investigated the effect of soluble Ca on the speciation of Pb in phosphate-amended soils. A calcareous soil was amended in sequence with soluble phosphate (0 and 299 mg kg(-1) P), calcium nitrate (0, 200, and 400 mg kg(-1) Ca), and/or lead nitrate (0 and 1000 mg kg(-1) Pb) and incubated for 50 d. Extractable Ca was relatively similar across all samples, with a minor reduction in Ca release for treatments amended with P possibly from the formation of Ca-phosphate minerals. Olsen-P extractability from P-added treatments was highest in the non-Pb-amended soils and was about 40% lower when Pb was added as a result of Pb-phosphate formation. In the absence of P, diethylene triamine pentaacetic acid (DTPA)-Pb extractability increased with increasing Ca amendment; however, in the P-amended treatments, DTPA-Pb decreased with increasing Ca addition. X-ray absorption spectroscopy results of the Pb spiked soils indicate that adsorbed Pb is the primary phase (up to 92%) in non-P-amended soils with minor distribution to hydrocerussite and Pb-phosphate phases. In the P-amended treatments, Pb speciation shifted to Pb-phosphate [chloropyromorphite and Pb-3(PO4)(2)] (42-48%) and adsorbed Pb (44-50%). As Ca concentration increased in the P-amended soils, Pb-phosphate speciation moved from combined chloropyromorphite and Pb-3(PO4)(2) (0 mg kg(-1) Ca) to exclusively chloropyromorphite. The study demonstrates that soluble Ca enhances Pb immobilization with P amendments.
Li, LP,Scheckel, KG,郑黎荣；Zheng, LR,et al. Immobilization of Lead in Soil Influenced by Soluble Phosphate and Calcium: Lead Speciation Evidence[J]. JOURNAL OF ENVIRONMENTAL QUALITY,2014,43(2):468-474.
Li, LP,Scheckel, KG,郑黎荣；Zheng, LR,Liu, GT,Xing, WQ,&Xiang, GQ.(2014).Immobilization of Lead in Soil Influenced by Soluble Phosphate and Calcium: Lead Speciation Evidence.JOURNAL OF ENVIRONMENTAL QUALITY,43(2),468-474.
Li, LP,et al."Immobilization of Lead in Soil Influenced by Soluble Phosphate and Calcium: Lead Speciation Evidence".JOURNAL OF ENVIRONMENTAL QUALITY 43.2(2014):468-474.